Electric circuit breaker of the gas-blast type



Dec. 12, 1944. D. F. AMER ETAL 3 5 ELECTRIC CIRCUIT BREAKER OFTHEGAS-BLAST TYPE Filed Sept. 29, 1942 V& 9% y\ D2 F k & Q 3M 645'5M5T mM GAS-8145f La DONALD F. AMER c ML WALTER H-WEBB I Aitorney PatentedDec. 12, 1944 ELECTRIC CIRCUIT BREAKER OF THE 7 GAS-BLAST TYPE.

Donald Foster Amer and Walter Henry Webb, Newcastle-on-Tyne, England,assignors to A. Reyrolle & Company Limited, Hebburn-on- Tyne, England, acompany of Great Britain Application September 29, 1942, Serial No.460,161 In Great Britain September 25, 1941 7 Claims.

This invention relates to an electric circuitbreaker of the kind inwhich a blast of deionising gas is caused to flow through a nozzle toassist in extinguishing the arc. In such circuit-breakers the arc isusually drawn out by relative movement of the arcing contacts, but forefficient operation it is desirable for the nozzle to be of relativelysmall size, and this gives rise to difiioulty in cases where the normalcurrentcarrying capacity required involves comparatively large contactsurfaces.

The present invention has for its object to avoid this difficulty and atthe same time to afford increased speed and certainty of operation.

The circuit-breaker according to the invention comprises a pair of fixedarcing contacts one of which is constituted by or is situated at andconnected to the low pressure end of the nozzle itself whilst the otheris supported from the high pressure side of the nozzle, and a movablebridging contact member which normally bridges the gap between the fixedarcing contacts or members electrically connected thereto and by whosemovement the arc is initially formed on the high pressure side of thenozzle, the are being blown by the gas-blast so that one are root movesalong the nozzle from the high pressure end to the low pressure endthereof and the arc is caused to take up a position favourable to arcextinction extending between the arcing contacts.

The fixed arcing contact supported from the high pressure side of thenozzle is conveniently constituted by the end of a rod or tube disposedsubstantially in alignment with the nozzle axis, and in this case thefixed arc-initiating contact, with which the bridging contact membercooperates may be constituted by the arcing contact rod or tube or by atube surrounding it and electrically connected to it. Alternatively thebridging contact member itself may be constituted by a tube surroundingand electrically connected to the arcing contact rod or tube. Thebridging contact member preferably moves in a direction substantiallyparallel to the nozzle axis.

Two convenient practical constructions according to the invention areillustrated by way of example in longitudinal section respectively inthe two figures of the accompanying drawing.

In the arrangement of Figure 1, the circuitbreaker is enclosed within acasing A of generally cylindrical form, to one end of which gas underpressure is introduced, when required, from a suitable reservoir, whilstthe other end serves for the discharge of the gases. At a suitableposition in the length of the casing A a metal nozzle B divergingtowards the discharge end is mounted in a metal housing 13 secured inthe casing A, and the inner surface B of such housing is formed as acylinder in which can slide a piston C carrying a bridging contactmember 0 in the form of a group of inwardly spring-pressed contacts.This piston C is moved by the gas pressure in a direction towards thedischarge end of the casing against the action of a spring C and thenozzle B is provided with an external contact surface B with which thebridging contact member C always remains in engagement throughout thepiston stroke.

In the normal closed position of the circuitbreaker the bridging contactmember 0 serves to bridge the gap between the nozzle B and a fixed tubeD mounted on the high pressure side of the nozzle in axial alignmenttherewith. This tube D surrounds and is connected by webs D to a centralrod D whose end D nearest the nozzle B constitutes one of the arcingcontacts of the circuit-breaker. The other arcing contact is constitutedby the low pressure end of the nozzle B itself, the two arcing contactsthus both being fixed at an appropriate distance apart, the gap betweenthem or between members electrically connected thereto normally beingclosed by the bridging contact member C.

- When it is desired to open the circuit-breaker, gas under pressure isadmitted to the casing A and acts on the piston C to drive it towardsthe discharge end of the casing within the metal housing 13 thusbreaking the connection between the tube D and the bridging contactmember and drawing out an are between them. The gas-blast acts on thisare immediately it is formed and tends to blow it through the nozzle B.One arc root remains anchored on the arcing contact constituted by theend D of the rod D whilst the other are root is blown across from thebridging contact member C on to the high pressure end of the nozzle Band thence along the nozzle surface to the second arcing contact at thelow pressure end. In this position the arc will be to some extent bowedout through the nozzle and its main length, at least, will lie more orless along the axis of the nozzle in a position favourable to areextinction by the gasblast.

The arrangement of Figure 2 shows a modified arrangement of the arcingcontacts. The casing A, the nozzl B and metal housing B and the bridgingcontact member C and its piston C and spring C are arranged as inFigure 1. The tube D and rod D are however replaced in this modificationby a simple rod F, with which the bridging contact member C normallyengages. The are is initially formed between the contact member C andthe rod F, and is at once blown through the nozzle by the gas-blast andi transferred thereby to the two arcing contacts, one of which isconstituted by a tip F on the end of the rod F. The other arcing contactmay again be constituted by the low pressure end of the nozzle B, or (asshown) by a separate contact B centrally mounted at the low pressure endof the nozzle and connected thereto by webs B The gap between the fixedarcing contacts is chosen to suit the conditions of the circuit on whichthe circuit-breaker is to be installed, and for voltages below say11,000 volts, it is convenient to extend the arcing tip F as shown inFigure 2, to a position fairly close to the second 2 arcing contact.

The operation of this arrangement will be at once clear from thedescription above given of that for the arrangement of Figure 1, and itwill be realised that the tube D and rod D of Figure l or the simple rodF of Figure 2 may be replaced by a simple tub D without the central rod(the front edge of the tube then acting as arcing contact). The use ofthe open tube D, with or without the central rod, has the advantage thatgas can flow through the tube as well as outside it, thus improving theaction of the gas-blast on the arc in the nozzle,

The use of an open tube, with its edge acting as arcing contact has thefurther advantage of enabling the invention to be combined with that ofthe concurrent United States of America patent application Serial No.460,160 in the names of the present applicants. In such case a centralrod similar to the rod D is provided but is insulated from the tube Dand connected thereto through a resistance, which comes into action whenthe arc is established between the end of such central rod and the lowpressure end of the nozzle (or the separate contact B if employed) sothat the arc current is then limited by the series resistance and isreadily and easily extinguished by the gas-blast.

It will be appreciated that the foregoing constructions have beendescribed by way of example only and that the invention can be carriedinto practice in other ways.

What we claim as our invention and desire to secure by Letters Patentis:

1. An electric circuit-breaker, including in combination a nozzle ofconducting material, means whereby a blast of deionising gas is causedto flow through the nozzle, a pair of fixed arcing contacts, one ofwhich is situated at the low pressure end the nozzle, means forsupporting the other fixed arcing contact from the high pressure side ofthe nozzle, a fixed arc initiating contact electrically connected tosuch other arcing contact, a movable arc initiating contact permanentlyconnected electrically to the nozzle and normally engaging with thefixed arc initiating contact and thereby bridging the electrical gapbetween the two arcing contacts, spring means for urging the movablecontact towards its normal position, and a piston carried by the movablecontact and exposed to the pressure of the gas-blast It'll against thespring action whereby such gas pressure causes the movable contact tomove remaining connected to the nozzle but breaking contact with thefixed arc initiating contact and thereby drawing out the arc on the highpressure side, the arc being blown by th gas-blast so that one are rootmoves along the nozzle from the high pressure end to the low pressureend thereof and the arc is caused to take up a position favorable to areextinction extending between the two fixed arcing contacts.

2. An electric circuit-breaker as claimed in claim 1, in which the fixedarcing contact at the the low pressure end of the nozzle is constitutedby part of the nozzl itself.

3. An electric circuit-breaker as claimed in claim 1, in which thearcing contact supported from the high pressure side of the nozzle isconstituted by the end of a rod-like member disposed substantially inalignment with the nozzle axis.

4. An electric circuit-breaker as claimed in claim 1, in which the fixedarcing contact supported from the high pressure side is constituted bytheend of a rod disposed substantially in alignment with the nozzleaxis, and the fixed arc-initiating contact is constituted by part of atube surrounding such rod and electrically connected thereto.

5. An electric circuit-breaker as claimed in claim 1, including meansmounting the movable contact for displacement substantially parallel tothe nozzle axis and generally in the direction of the gas flow throughthe nozzle.

6. An electric circuit-breaker, including in combination a nozzle ofconducting material, means whereby a blast of deionising gas is causedto flow through the nozzle, a pair of fixed arcing contacts, one ofwhich is situated at the low pressure end of the nozzle, is disposedgenerally centrally in the gas stream flowing through the nozzle and iselectrically connected to the nozzle, mean for supporting the otherfixed arcing contact from the high pressure side of the nozzle, a fixedarc-initiating contact electrically connected to such other arcingcontact, a movable arcinitiating contact permanently connected to thenozzle and normally engaging with the fixed arcinitiating contact andthereby bridging the electrical gap between the two arcing contacts,spring means for urging the movable contact towards its normal position,and a piston carried by the movable contact and exposed to the pressureof the gas-blast against the spring action whereby such gas pressurecauses the movable contact to move while remaining connected to thnozzle but breaking contact with the fixed arc-initiating contact andthereby drawing out the are on the high pressure side, the are beingblown by the gasblast so that one are root moves along the nozzle fromthe high pressure end to the low pressure end thereof and th arc iscaused to take up a position favorable to arc extinction extendingbetween the two fixed arcing contacts.

7. An electric circuit-breaker as claimed in claim 1 in which themovement of the movable contact takes place substantially parallel tothe axis of the nozzle generally in the direction of the gas flowthrough the nozzle.

DONALD FOSTER AMER. WALTER HENRY WEBB.

